U.S. patent number 4,026,392 [Application Number 05/650,733] was granted by the patent office on 1977-05-31 for snap-acting over-center chain saw safety brake and method of operation thereof.
This patent grant is currently assigned to McCulloch Corporation. Invention is credited to Sidney Hirschkoff.
United States Patent |
4,026,392 |
Hirschkoff |
May 31, 1977 |
Snap-acting over-center chain saw safety brake and method of
operation thereof
Abstract
A chain saw safety brake including a snap-acting, over-center
actuating mechanism. A chain saw safety brake and method of
operation characterized by an actuation accelerator interposed
between a brake mechanism and a brake actuating mechanism. A
biasing means is operable to bias the brake actuating means toward
a nonactuating position with a relatively lower biasing force. The
biasing means is operable to bias the brake actuating means toward
an actuating position with a relatively higher biasing force.
Inventors: |
Hirschkoff; Sidney (Los
Angeles, CA) |
Assignee: |
McCulloch Corporation (Los
Angeles, CA)
|
Family
ID: |
27058389 |
Appl.
No.: |
05/650,733 |
Filed: |
January 20, 1976 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
515046 |
Oct 15, 1974 |
3934345 |
|
|
|
Current U.S.
Class: |
188/166; 74/97.1;
192/80; 30/381; 188/77R; 192/17R |
Current CPC
Class: |
B27B
17/083 (20130101); F16D 49/10 (20130101); F16D
59/02 (20130101); Y10T 74/18864 (20150115) |
Current International
Class: |
B27B
17/08 (20060101); B27B 17/00 (20060101); F16D
49/10 (20060101); F16D 59/02 (20060101); F16D
49/00 (20060101); F16D 59/00 (20060101); B60T
013/04 () |
Field of
Search: |
;188/166,167,77R
;192/80,89R ;74/97 ;30/381,383 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Halvosa; George E. A.
Attorney, Agent or Firm: Burns, Doane, Swecker &
Mathis
Parent Case Text
This is a division, of application Ser. No. 515,046, filed Oct. 15,
1974, now U.S. Pat. No. 3,934,345.
Claims
What is claimed is:
1. A chain saw safety brake comprising:
brake means including a brake element and spring biasing means;
brake actuating means directly movably engaged with said brake
means; and
actuation accelerator means operably interposed between said brake
actuating means and said brake means and operable to effect a
faster rate of brake actuation than would result from said movable
engagement between said brake actuating means and said brake
means;
said spring biasing means being operable to
bias said brake actuating means toward a nonactuating position with
a first biasing force, and
bias said brake actuating means toward an actuating position with a
second biasing force which is higher than said first biasing
force.
2. In a method of safety-braking a chain saw, wherein said chain
saw includes
brake means including a brake element and spring biasing means,
and
brake actuating means directly movably engaged with said brake
means,
the improvement comprising:
operably interposing actuation accelerator means between said brake
actuating means and said brake means and employing said accelerator
means to effect a faster rate of brake actuation than would result
from said movable engagement between said brake actuating means and
said brake means;
biasing said brake actuating means toward a nonactuating position
with a first biasing force; and
biasing said brake actuating means toward an actuating position
with a second biasing force that is higher than said first biasing
force.
3. A chain saw safety brake comprising:
brake means;
brake activating means, including biasing means for activating said
brake means, said brake activating means being movable from a first
position in which said biasing resists activation of said brake
means, to a second position in which said biasing means activates
said brake means;
handle means movable to a brake actuating position and
including:
first surface means engageable with said brake activating means at
a first location thereof for shifting said brake activating means
from its first position to its second position in response to
movement of said handle means to its brake actuating position;
and
accelerator surface means engageable with said brake activating
means at a second location thereof for shifting said brake
activating means from its first position to its second position in
response to movement of said handle means toward a brake actuating
means, at a faster rate than that produced by said first
surface;
said brake activating means being arranged so that in said second
position thereof said biasing means activates said brake means with
a force that is greater than the force with which it resists
activation when said brake activating means is in said first
position.
4. A safety brake according to claim 3 wherein said brake
activating means includes a guide rod, and said biasing means
includes a spring biasing said guide rod against said first
surface.
5. A safety brake according to claim 3 wherein said brake
activating means includes a cam follower, said first surface means
comprises a cam surface whose orientation is altered by movement of
said handle means, and said accelerator surface means comprises a
lug carried by said handle means.
6. A safety brake according to claim 5 wherein said handle means is
mounted for pivotal movement about a pivot axis, said lug being
spaced a greater distance from said axis than the spacing between
said cam surface and said pivot axis when said handle means is out
of said actuating position.
7. A safety brake according to claim 3 wherein said first surface
means is operable to shift said brake activating means to said
first position in response to movement of said handle means from
said brake actuating position, said handle means further including
third surface means engageable with said brake activating means at
a third location thereof for shifing said brake activating means
from said second to said first position in response to movement of
said handle means from said brake actuating position, at a faster
rate than that produced by said first surface.
8. A chain saw safety brake comprising:
a housing;
brake means;
brake activating means, including biasing means, for activating
said brake means, said brake activating means being movable from a
first position in which said biasing means resists activation of
said brake means, to a second position in which said biasing means
activates said brake means;
handle means movable to a brake actuating position and operably
connected to said brake actuating means to alter the orientation
thereof in response to movement of said handle means to said brake
actuating position;
said housing including:
a first surface engageable with said brake activating means at a
first location thereof to cause shifting of said brake activating
means from its first position to its second position in reponse to
movement of said handle means to its brake actuating position;
and
an accelerator surface engageable with said brake activating means
at a second location thereof to cause shifting of said brake
activating means from its first position to its second position in
response to movement of said handle means toward a brake actuating
means, at a faster rate than that produced by said first
surface;
said brake activating means being arranged so that in said second
position thereof said biasing means activates said brake means with
a force that is greater than the force with which it resists
activation when said brake activating means is in said first
position.
9. A safety brake according to claim 8 wherein said brake
activating means includes a guide rod and said biasing means
includes a spring biasing said guide rod against said first
surface.
10. A safety brake according to claim 9 wherein said brake
activating means includes a cam follower, said first surface
comprises a cam surface, said guide rod having its orientation
altered in response to movement of said handle means to enable said
cam surface to cause shifting of said cam follower under the urging
of said spring, said accelerator surface means comprising a lug
carried by said housing.
11. A safety brake according to claim 10 wherein said handle means
is mounted for pivotal movement about a pivot axis, said lug being
spaced a greater distance from said axis than the spacing between
said first suface and said pivot axis when said handle means is out
of said actuating position.
12. A safety brake according to claim 8 wherein said first surface
is operable to shift said brake activating means to said first
position in response to movement of said handle means from said
brake actuating position, said housing further including third
surface means engageable with said brake activating means at a
third location thereof for causing shifting of said brake
activating means from said second to said first position in
response to movement of said handle means from said brake actuating
position, at a faster rate than that produced by said first
surface.
Description
GENERAL BACKGROUND, OBJECTS AND SUMMARY OF INVENTION
With continuing emphasis being placed upon the improvement of
safety conditions in relation to the use of chain saws, it has
become increasingly important to protect chain saw operators from
injuries resulting from "kickbacks" of chain saws or from
situations where operators losing their grip on chain saw handles
such that their hands are brought into engagement with chain saw
cutter chains.
Several techniques have been developed in the past in an endeavor
to improve chain saw safety and protect operators from injuries
when events such as this occur.
All this notwithstanding, there has persisted in the art a need to
improve the efficiency and reliability of such safety
mechanisms.
Accordingly, it is a specific object of the present invention to
provide a chain saw safety brake which is snap-acting and operated
via an accelerating mechanism so as to produce a cutter chain
braking action in an extremely rapid manner.
It is a further object of the present invention to accomplish such
a rapidity of breaking with a minimized movement of an actuating
member or safety handle.
Yet another object of the invention is to provide a chain saw
safety brake actuating mechanism wherein an intensified biasing
force is created when the actuating mechanism is moved to a brake
actuating position.
It is likewise an object of the invention to provide such
improvements in the art as heretofore described concurrent with the
attainment of relative structural simplicity and reliability and
the minimizaton of alterations to conventional chain saw
structures.
In accomplishing at least some of these objectives, the present
invention contemplates a method of actuating a chain saw safety
brake which is characterized as follows.
The method of this invention involves the safety braking of a chain
saw which includes brake means and brake actuating means movably
engaged with said brake means. The inventive method entails:
Operably interposing actuation accelerator means between the brake
actuating means and the brake means and employing this accelerator
means to effect a faster rate of brake actuation than would result
from said movable engagement between the brake actuating means and
the brake means;
Biasing the brake actuating means toward a nonactuating position
with a relatively lower biasing force; and
Biasing the brake actuating means toward an actuating position with
a relatively higher biasing force.
Likewise, the invention contemplates unique combinations of
apparatus means which coact to effect the method steps heretofore
described.
Moreover, the invention herein presented contemplates a variety of
structural embodiments characterized by a resiliently biased,
snap-acting, over-center actuating mechanism.
In describing the invention, reference will be made to these
presently preferred embodiments by way of example and with
reference to appended drawings. However, it will be understood that
the reference to preferred embodiments will be by way of example
only and not by way of restricting the scope of the present
invention.
DRAWINGS
Presently preferred embodiments of the invention are illustrated in
the appended drawings. In these drawings
FIG. 1 provides a fragmentary, partial elevational view of that
portion of a chain saw immediately associated with the safety brake
mechanism of the present invention and showing the chain saw in a
non-braked condition;
FIG. 2 provides an enlarged fragmentary elevational view of the
safety brake mechanism featured in FIG. 1, but illustrating the
chain saw in a braked condition;
FIG. 3 provides a sectional view of the FIG. 1 safety mechanism as
viewed along the section line 3--3 of the FIG. 2, brake actuated
condition;
FIG. 4 schematically illustrates a somewhat modified form of the
safety brake mechanism which is illustrated in FIGS. 1-3,
illustrating the modified form in an actuated or braked
condition;
FIG. 5 provides a fragmentary, elevational view of a chain saw
portion, generally related to that shown in FIG. 2, but depicting a
still further alternative format of the present chain saw braking
concept, with this alternative structure being depicted in a
non-braking condition;
FIG. 6 provides a sectional view of the FIG. 5 embodiment as viewed
along section line 6--6 of FIG. 5; and
FIG. 7 depicts the FIG. 5 safety brake in the context of the chain
saw portion as generally shown in FIG. 1, depicting this format
somewhat schematically, illustrating a chain saw centrifugal clutch
different than that incorporated in FIG. 1, and depicting the FIG.
5 chain saw in an actuated or braked condition.
With the content of the drawings having been generally described,
it now becomes appropriate to consider individual structural
details of the invention.
GENERAL DESCRIPTION OF INVENTION
In describing the chain saw safety brake of the present invention,
reference will first be made to exemplary embodiments, showing by
way of example only, representative chain saws and chain saw drive
mechanisms with which the present invention is intended to be
practiced.
OVERALL CHAIN SAW STRUCTURE
FIGS. 1 and 7 each illustrate representative chain saw structures
with which the present invention is intended to be practiced.
FIG. 1 depicts a chain saw 1 generally as shown in Frederickson
U.S. Pat. No. 3,542,095, issued Nov. 24, 1970, the disclosure of
which is herein incorporated by reference. Chain saw 1 includes
chain saw engine means 2 and chain saw cutter chain means 3.
Chain saw 1 further includes chain saw driving means 4 which is
operable to provide a driving connection between the chain saw
engine means 2 and the chain saw cutter means 3.
The chain saw driving means 4 may include a centrifugal clutch 5,
generally as depicted in Collins U.S. Pat. No. 3,385,411 issued May
28, 1963, the disclosure of which is herein incorporated by
reference.
Clutch 5 includes centrifugally responsive, clutch shoe means 6
operable to be driven by the engine means 2, and clutch drum means
7 drivingly connected with the chain saw cutter chain 5 means and
operable to be centrifugally engaged by the clutch shoe means
6.
Saw 1 additionally includes chain saw hand grip means 8 which may
be generally like the hand grip means featured in Frederickson U.S.
Pat. No. 3,542,095 or modified somewhat, as shown in FIG. 1, to
omit side portion 39 of the Frederickson handle.
The FIG. 7 chain saw corresponds generally to that shown in FIG. 1
and its basic components have been assigned reference numerals
equivalent to those of FIG. 1, but increased by 100.
However, by way of example, it will be noted that the FIG. 7 chain
saw 101 may include a hand grip means 108 corresponding generally
to that generally depicted in Loop U.S. Pat. No. 3,678,973, the
disclosure of which is herein incorporated by reference.
Moreover, chain saw 101 may include a centrifugal clutch 105
generally as shown in Frederickson U.S. Pat. No. 3,768,611, the
disclosure of which is herein incorporated by reference.
For definitional purposes, the term "chain saw" will be used to
define a chain saw structure independent of the chain saw safety
brake of the present invention.
With the chain saw context of the invention having been discussed,
by way of example only, it now becomes appropriate to consider
structural and method aspects of the present safety brake
invention.
CHAIN SAW SAFETY BRAKE -- FIRST EMBODIMENT
A first preferred embodiment of the invention is illustrated in
FIG. 1 through 3.
As shown in FIGS. 1 to 3, chain saw 1 is associated with a chain
saw safety brake 9.
Brake 9 includes safety handle means 10, generally as depicted in
Dooley U.S. Pat. No. 3,839,795 issued Oct. 8, 1974, the disclosure
of which is herein incorporated by reference.
Safety handle means 10 is operable to be engaged at transverse
portion 10a by movement of a chain saw operator's hand away from
the chain saw hand grip means 8 during a "kickback" or when the
operator's hand slips off of hand grip 8 and moves toward cutter
chain 3.
A pivot means 11 pivotally supports the safety handle means 9 on
the chain saw 1.
Brake 9 includes a brake band means 12 which at least partially
encircles clutch drum means 7 as shown in FIG. 1. Band 12, which
may be fabricated of a spring steel band, is operable to be
disposed in
a first, relatively expanded, brake band condition shown in FIG. 1
permitting chain driving rotary movement of the clutch drum 7,
and
a second, relatively constricted, brake band condition shown in
FIG. 2 engaging and substantially preventing movement of the clutch
drum 7.
An anchor means or pin mounting 13 is connected with one hooked end
14 of the brake band 12 and secures this one end 14 of the brake
band to the engine housing 15 of the chain saw 1.
A connecting means or other pin mounting 16 secures another end 17
of the brake band 12 to a portion 10b of the safety handle 10,
which portion 10b is spaced from the safety handle pivot 11a. With
this arrangement, movement of the safety handle 10 away from the
hand grip means 8, and the first safety handle means position
depicted in FIG. 1 providing the first, relatively expanded brake
band condition, will move the connecting means 16 relative to the
anchor 13 means and position the safety handle 10 at a second
safety handle means position depicted in FIG. 2 so as to constrict
or tighten the brake band 12 about clutch drum 7 and dispose the
brake band 12 in a second, relatively constricted, condition shown
in FIG. 2.
Brake means 9 further includes a resilient biasing means 18
comprising
a first, block-like mounting means 19 which is pivotally secured by
pivot mount 20 to the engine housing 15 of chain saw 1,
a coil spring 21 which has one end 21a which engages one end 22 of
the first mounting means 19,
a guide rod 23 which extends telescopingly through the coil spring
21 and a passage 24 of the first mounting means 19, and
a second, clevis-like mounting means 25 biasingly engaged at end 26
by another end 21b of the coil spring 21 and connected with the
guide rod 23 by rod connection 27.
An over-center connecting means operably interconnects the biasing
means 18 and the safety handle 10 and includes
a cam surface 29 carried by the safety handle 10 and extending
transversley of a radius 11a of the safety handle pivot 11 on
opposite sides of this radius, and
a rod-like, bearing or cam follower means 30 carried by the legs
25a and 25b of the second mounting means 25 and disposed in sliding
engagement with the cam surface 29, with the coil spring 21
biasingly urging the cam follower 30 into sliding engagement with
the cam surface 29 and the legs 25a and 25b being movably disposed
adjacent opposite edges 29a and 29b of the cam surface 29.
As shown in FIG. 2, the cam surface 29 may comprise a somewhat
convex surface carried by the safety handle 10, disposed in
alignment with a plane extending longitudinally of the chain saw 1,
and curving about pivot axis 11.
As is further shown in FIG. 2, the safety brake additionally
includes a cam follower retaining means 31 which cooperates with
the cam surface 29 to define a movement restricting enclosure, or
slot 32 constraining said cam follower 30.
The cam follower 30, when engaged with a first portion 29c of the
cam surface 29 depicted in FIG. 2 which is located on one side of
the radius 11a, as shown in FIG. 1, is operable to resiliently bias
the safety handle 10 towards the hand grip 8 and the first safety
handle means position effecting the first, relatively expanded
condition of said brake band means. In this "cocked" condition, the
chain saw brake is disposed for normal chain saw operaton.
The cam follower 30, when engaged with a second portion 29d
depicted in FIG. 1 of the cam surface 29 on another side of the
radius 11a, as shown in FIG. 2, is operable to resiliently bias the
safety handle 10 toward the second safety handle means position
effecting the second, relatively constricted condition of said
brake band means. In this condition, effected by an operator's hand
leaving grip 8 and engaging handle portion 10a so as to push handle
10 toward the cutter chain 3, the clutch drum 7 and cutter chain 3
are braked.
As will now be appreciated, the cooperation between braking means
18 and safety handle 10 affords a resiliently biased, snap-acting,
over-center mode of movement of handle 10 between the FIG. 1
"cocked" and FIG. 2 "braked" positions and vice versa.
The biasing means 18 cooperates with the safety handle 10, in the
first, safety handle means position of engagement between said cam
follower 30 and the cam surface means 29 shown in FIG. 1, to
provide a relatively shorter lever arm 33 through which the biasing
means 18 acts resiliently on the safety handle 10 to resiliently
bias this safety handle 10 toward the hand grip 8 and the first,
safety handle means position of FIG. 1. This means that "recocking"
of the safety handle 10 from the FIG. 2 to the FIG. 1 position may
be relatively easily effected.
The biasing means 18 cooperates with the safety handle 10, in the
second, safety handle means position of engagement between said cam
follower 30 and the cam surface 29, to provide a relatively longer
lever arm 34 through which the biasing means 18 acts resiliently on
the safety handle 10 to resiliently bias this safety handle 10 away
from the hand grip 8 and toward the second, safety handle means
position of FIG. 2. This means that an intensified brake setting
force will result when an operator's hand moves handle 10 to the
brake setting position of FIG. 2.
A first, accelerator lever means 35 is carried by the safety handle
10 and comprises a lug-like plate 35a carried by lever arm 35b as
to be engageable with the bottom side of clevis 25. Plate 35a may
have a width straddling clevis 25, as shown in phantom line in FIG.
3. Lever 35 is disposed on the bottom side of radius 11a and the
second mounting means or clevis 25 and is operable to engage the
bottom side of clevis 25 at a location spaced radially outward from
the cam follower 30 in relation to pivot axis 11. The first
accelerator lever means 35 is thus operable to induce
counterclockwise movement of the cam follower 30 (as shown in FIG.
1) relative to the cam surface 29, toward said second portion 29d
of the cam surface 29 in response to clockwise pivoting movement
(as shown in the drawings) of the safety handle 10 toward the
second safety handle means position of FIG. 2 at a faster rate than
would result only or merely from direct sliding engagement of the
cam follower 30 and the cam surface 29 during such pivoting
movement. This means that an accelerated, over-center, snap-acting
cooperation between biasing means 18 and actuating handle 10 will
occur when an operator's hand pushes on handle portion 10a and
effect very rapid brake setting movement of handle 10 with less
handle movement than would be otherwise required.
A second, accelerator lever means 36 is carried by the safety
handle 10 and includes a clevis engaging plate 36a and a lever arm
36b essentially like those of lever means 35. However, lever 36 is
disposed on the top side of the radius 11 and the second mounting
means or clevis 25 and is operable to engage the top side of the
clevis 25 at a location spaced radially outward from the cam
follower 30, in relation to pivot 11. The second accelerator lever
36 is operable to induce clockwise movement of cam follower 30 (as
shown in FIG. 2) relative to the cam surface 29 toward the first
portion 29c of the cam surface 29 in response to counterclockwise,
handle recocking, pivoting movement of safety handle 10 toward the
first safety handle means position of FIG. 1 at a faster rate than
would result only or merely from direct engagement of the cam
follower 30 and the cam surface 29 during such pivoting, recocking
movement. This means that an accelerated recocking of handle 10 may
be effected, with counterclockwise recocking force being exerted on
handle 10 for a shorter increment of handle movement than would
otherwise be required.
CHAIN SAW SAFETY BRAKE -- SECOND EMBODIMENT
A second embodiment of the chain saw safety brake of the present
invention comprising a somewhat modified form of the FIGS. 1- 3
embodiment is illustrated in FIG. 4.
The FIG. 4 embodiment is substantially identical to the FIGS. 1- 3
embodiment except that the retaining means 31 is omitted. In other
words, cam surface 29 is "open" rather than "enclosed".
CHAIN SAW SAFETY BRAKE -- THIRD EMBODIMENT
The first and second chain saw safety brake embodiments were
characterized by arrangements where the actuating cam surface is
carried by the safety handle and the first mounting means 19 of the
biasing means 18 is connected with the chain saw engine housing 15.
In these embodiments, the biasing means may extend along the side
of the chain saw, generally across the chain saw centrifugal clutch
5, as depicted in FIGS. 1 through 4.
In a third embodiment of the present invention, depicted generally
in FIGS. 5- 7, the biasing means extends upwardly generally along
the chain saw hand grip means and the safety handle. In this third
embodiment, the cam surface means is mounted on the engine housing
while the first mounting means of the biasing means is carried by
the safety handle.
As will be recalled, components of the FIGS. 5- 7 embodiment are
identified by reference numerals corresponding to equivalent
components of the FIGS. 1- 4 embodiments, increased by 100.
Inasmuch as the mode of cooperation between the components of the
FIGS. 5- 7 embodiment is substantially the same as the mode of
cooperation between the FIGS. 1- 4 embodiment's components, and
this is self-evident from the drawings, it is not deemed necessary
to reiterate structural details in relation to FIGS. 5- 7.
Suffice it to say that in FIGS. 5- 7, the cam surface 129 is
carried by the engine housing 115 of chain saw 101 and the first
mounting means 119 is pivotally secured by pivot 120 to safety
handle 110.
Moreover, instead of the accelerating lever means 135 and 136 being
disposed above and below the clevis 125 as in the case of the
disposition of elements 35, 36 and 25, lever means 135 is disposed
to the right side of clevis 125, with lever means 136 being
disposed on the left side, as illustrated in FIGS. 5- 7.
It might also be noted that the extremity of the "cocked" position
of handle 10, as depicted in FIG. 1, may be determined by the
biasing force of spring 21 or by engagement of handle 10 with
suitable stop means carried by the chain saw body or hand grip
means. In the FIGS. 5- 7 embodiment, this "cocked" position
extremity is defined by engagement of handle 110 with hand grip
108, as depicted in FIGS. 5 and 6.
SUMMARY OF ACTUATION CHARACTERISTICS
As will now be apparent, this invention is concerned with a method
of safety-braking a chain saw, wherein the chain saw includes brake
means and brake actuating means movably engaged with said brake
means.
Characterizing features of the invention involve:
operably interposing actuation accelerator means, such as the
described accelerating lever means, between the brake actuating
means and the brake means and employing such accelerator means to
effect a faster rate of brake actuation than would result from said
movable engagement between said brake actuating means and said
brake means alone;
biasing the brake actuating means toward a nonactuating position
with a relatively lower biasing force; and
biasing the brake actuating means toward an actuating position with
a relatively higher biasing force.
The invention is also independently characterized by an
over-center, snap-acting, cocking and braking mechanism.
SUMMARY OF MAJOR ADVANTAGES AND GENERAL SCOPE OF INVENTION
The resiliently biased, snap-acting, over-center actuating
mechanism described in connection with each of the three
embodiments set forth in this application produces several unique
advantages.
In the first instance, it will be noted that the lever means
associated with the cam surface means causes the cam follower means
to translate along the cam surface means faster than this movement
would occur if the lever means were not present. This insures
unusually rapid or accelerated brake setting when the safety handle
is tripped or engaged by an operator's hand and further insures
brake actuating and handle cocking movement in response to
relatively short increments of movement of the safety handle.
Moreover, the unique, over-center character of the actuating
mechanism produces a longer lever arm through which biasing force
is exerted on the safety handle when the handle is moved toward the
brake actuating position. This phenomenon produces an intensified
braking force. The itensified braking force in conjunction with the
accelerated braking action is believed to materially improve the
rapidity and efficiency of stopping of the cutter chain of the
chain saw so as to enchance overall safety conditions.
Independent of these particular and significant advantages, it is
believed that the structural arrangements heretofore described are
also characterized by unique simplicity, ruggedness, and
reliability. It will also be appreciated that these arrangements
enable safety brake mechanisms to be installed with minimal
modification of conventional chain saw structures and without
interfering with conventional drive chain arrangements.
Proposals have been heretofore offered which have significantly
advanced the state of chain saw safety. These proposals are
disclosed in Moore United States application Ser. No. 109,574, now
U.S. Pat. No. 3,739,475, issued June 19, 1973; Moore United States
application Ser. No. 294,366, now U.S. Pat. No. 3,793,727, issued
Feb. 26, 1974; and Dooley United States application Ser. No.
354,776, now U.S. Pat. No. 3,839,795, issued Oct. 8, 1974, all
assigned to the assignee of the present invention.
Other chain saw safety proposals have been proferred as can be
seen, for example, in Gustafsson U.S. Pat. No. 3,776,331, issued
Dec. 4, 1973; Mattsson et al U.S. Pat. No. 3,664,390, issued May
23, 1972; Irgens U.S. Pat. No. 3,361,165, issued Jan. 2, 1965;
Kiekhaefer U.S. Pat. No. 2,610,657, issued Sept. 16, 1952; and
British Pat. No. 1,351,546, published May 1, 1974.
These prior art concepts notwithstanding, the accelerated and
intensified braking characteristics of the present invention are
considered to constitute a novel, unobvious, and advantageous
advance in the chain saw art.
Those skilled in the chain saw art and familiar with the present
disclosure may well envision alternative arrangements in addition
to those described and will recognize that the invention may be
practiced in a variety of structural formats and in connection with
a substantial variety of chain saws and chain saw drive mechanisms
and chain saw brake mechanisms, in addition to those illustrated.
In short, while additions, deletions, substitutions or
modifications in relation to the disclosed embodiments may be
effective in practicing the invention, such changes would be deemed
to fall within the purview of the present invention to the extent
encompassed by the appended claims.
* * * * *